Tsukishima's Experiment
by theasianwriter
Summary: It has already been a given that Tsukishima is blessed with intelligence and whenever he wants something, he always find a way to have it into his possession, and right now, a certain clumsy brunette who's been with him since forever suddenly took his interest and curiosity.
1. Chapter 1

_**A/N: Heeyy! It's been awhile since I wrote something and I finally came up with a Tsukkiyama multi-chaptered fic! YAY! This'll only be three chapters and I'll try to make it amusing and fun as much as I can. I think my writing's been a little rusty but I hope you enjoy this :)**_

 _ **Disclaimer: I do not own the characters used in this story. The plot is merely a product of my imagination.**_

 **The Sudden Behavior Change of Yamaguchi Tadashi**

* * *

So, when did it all begin?

It started like any other day at school, going early for morning practices, zoning out while their teacher babbles away with their lessons, hanging out with Tsukki on lunch break and end the day with pissing the hell out of Kageyama and Hinata on after school's practices.

The club didn't really change much after their senpais' graduation. They were now the ones leading and teaching their juniors. With Kageyama as the scary captain, Tsukki as the vice-captain who didn't really care much about them and their overly hyper ace who seems to light up whenever one of the first years all him 'Hinata-senpai', everything seems to be in order and the team gradually keeps on improving every step of the way.

Anyway, it began after almost all of the lot were heading home and they were the only ones left in the club room. Hinata dragged Kageyama with him, whispering that he needed Kageyama to loan him money because he spent all of his allowance treating the younger ones the other day.

With a huff and some muttering, Kageyama went along with Hinata and gave Tsukki the key, ordering him to lock up.

The air around them wasn't awkward yet, until Tsukki went up to him while he was still shirtless. Since he was facing the other way around, he really didn't see him coming.

"Hey, you done?"

The hairs on his nape rose when he felt Tsukki so close to him. Knowing Tsukki, he probably has something on his sleeve and he will probably be the one to experience what he planned.

"Uh- Y-Yeah. Just give me a sec." He hurriedly put on his shirt and avoided the feeling to cover his body. It's not that he's concious of his body or anything, he practices regularly but he can't get off the feeling that's somebody's ogling at him. Of course, that was silly because they were the only ones left here. Him and Tsukki.

Since their houses are not that far from each other, they walk to and from school together. It was already dark when they got out from the school's vicinity and due to Coach's Ukai new regimen that they're recently doing, they were dead beat and didn't really bother much to talk to each other.

Not that they always talk to each other that much. Tsukki sometimes prefers to just hang out with him and do things he typically do. And that setting is fine with him actually. Especially when Tsukki gets too engrossed with what he's doing and he can't help but to admire his friend's concentration.

They were quietly walking side-by-side. No words exchanged between them, but each content with just walking together. It was only a few blocks away from his house and Tsukishima would say good-bye to him and go to the adjacent street. Yamaguchi was waiting for his friend to take off his headphones and leave him with a curt "good-bye" when all of those didn't happen. Nope. Not even the taking off of headphones. Instead, Tsukki continued to walk to the direction of his house.

Yamaguchi stopped in his tracks, but Tsukishima kept on walking like nothing's wrong. Maybe he just seemed to caught up listening to his music?

After a few good feet, Tsukki noticed that he was the only one walking and looked back to check at him. He took off his headphones and walked back at him with a puzzled look.

Yamaguchi shrugged, "You're heading towards my house."

Tsukishima didn't answer him, instead he seemed like he found the answer to his questions. In fact, he was making what he's doing like the most obvious thing and Yamaguchi is such a snail to get it.

He wants to know what's going on inside Tsukki's head, but it's too complicated to think like Tsukki. Instead of figuring out what his friend wants, it might just backfire at him and give him a headache.

He didn't move a single inch from where he was and let Tsukki go to him. If Tsukishima wouldn't even utter a single sound, it looks like he has to push him to actually say something.

He made eye contact with him and didn't blink. God, they always do this. It's like Tsukki's special way of being stubborn.

"Tsukki, what do want?" He almost pleaded Tsukishima to just tell him straight out what he wants. His eyes were burning already and a sudden gust of wind passed them and it's stinging his eyes.

Yamaguchi, of course, wasn't foreign to Tsukki's little plans that always has ulterior motives, and he, Tsukishima Kei's most loyal friend has been and still is Tsukki's subject when he wants to test out something.

The first time Tsukki did that to him, he cried when he still didn't know that all of it was just a behavior experimentation, and he still cried when Tsukki told him, laughing and all that he didn't have leukemia. He just wants to know how he will react.

Tsukki faintly smirked but he never failed to see it, "It's dark, so I'm taking you home. We still have practice that'll probably turn into a match again and Kageyama would kill me if the team's pinch server would go missing."

Yamaguchi knows something's up, but he decided to play along. "You're overreacting, Tsukki." He lightly slapped him on the shoulder and started walking first.

Tsukishima followed right after him and strangely didn't put his headphones back. They started to walk in silence again, when they reached his house he turned back to Tsukki and smiled at him.

"Well, the pinch server's safe now, so you can relax," he tried laughing to ease the uneasiness he's feeling. "Thanks, Tsukki. Goodnight."

Instead of replying to him, Tsukki is still standing in front of him. He was staring at him like he was speculating something. Behind his rimmed glasses were eyes sparkling with mischief and plans yet to be conducted, and Yamaguchi was sure he was all part of that new plan Tsukki has.

"Yeah, goodnight."

Before anything could be done, Yamaguchi turned away and reached for their gate to go inside, but he was stopped by a sudden turn of his body and something warm and firm on his lips.

His eyes were still open and his mind couldn't seem to process the sudden turn of events. He stopped breathing a moment ago and only breathed again when those warm things on his lips stopped invading his personal space.

"Goodnight, Yamaguchi." Tsukki wiped something on the corner of his mouth with his thumb and walked away from his house.

Yamaguchi was left dumbfounded outside his house. He was unable to comprehend what happened and when he finally did, he touched his still swollen lips to verify if it really did happen.

When the pads of his fingers touched his lips, it throbbed and the presence of the lips that kissed him still lingered there.

If he's right about this. His best friend, Tsukishima Kei, had just kissed him not to long ago.

My God, Tsukki actually kissed him.

Yamaguchi was so shocked and baffled by what happened that he didn't eat dinner. He went to his room and and locked the door. He can't believe what just happened.

Is this part of Tsukki's little experiment with him once again? Well, if it is, it's not funny anymore.

It's not that he hasn't been kissed already. Over the span of his high school life, he dated girls and kissed them a couple of times, before those girls decided that he was too ordinary for their tastes and broke up with him.

But the way Tsukishima kissed him earlier wasn't similar on how he kissed his former girlfriends. Yamaguchi kossed them with such caution. It's like walking in eggshells, once he made a wrong move, it's game over, but with Tsukki, it wasn't the case. He kissed him so suddenly and hardly that he wasn't given the time to process what he had just done.

To be kissed by your long time friend was already shocking and confusing, but what terrifies him more is that this maybe or may not be the end of all this "experiment," as Tsukki calls it.

* * *

Guess who didn't sleep the other night? That's right, Yamaguchi.

Guess who also forgot to do their homework because he was thinking of some other things? Right, again. It's still Yamaguchi.

Guess who were late for their morning practice? Nope it isn't just Yamaguchi anymore. He has someone else with him and he hoped that it wasn't the case.

It was very rare for Tsukki to be late in their morning practices. Sure, he may piss Kageyama or Hinata a lot, but he was the sort of person who valued punctuality, and coincidentally, Yamaguchi still catched him changing.

"Morning, Tadashi." Tsukki glanced at him and went back on slipping of his gakuran.

"Morning, Tsuk-" Yamaguchi almost stopped dead on his tracks, but then continued walking to his shelf. "Morning." He managed to squeak.

Since when did Tsukki decided to call him on his first name and greeted him first thing in the morning? That was his thing and what Tsukki would usually do is grunt at him in reply. He really has something up on his sleeves, Yamaguchi decided.

He changed quietly and did it fast because he knows Kageyama will be all over them for the rest of their practice because they're late.

He thought that Tsukki has already gone off to practice, but much to his surprise, he was still in the room, waiting for him to finish changing.

"Let's go," he tried not to meet Tsukki's gaze but failed when he called him. He was ready to open the door, but winced when he was called

"Yamaguchi."

He slowly turned over and Tsukki was one inch farther away from his face. He stepped backwards until he hit the door behind his back, his left hand still gripping the knob.

"W-what's the matter, Tsukki?" He tried to avoid his face near Tsukishima's as much as he can but it seems like the farther he steps, Tsukki seems to make up for the distance left between them.

They stayed at that position for a couple of minutes, heck, don't ask him how long it is! He was busy making his breathing seem normal in front of Tsukki, because circumstances like this, makes it hard to breathe.

His knees were already shaking badly that he almost gave in to falling down. Luckily, Tsukki withdrew his face away from him and acted like nothing happened. Again!

Ahh, damn it! Why was he always making his life harder? He sighed and followed Tsukki outside.

As expected, as soon as they took a step inside the gymnasium, Kageyama glared at him then at Tsukishima. Hinata smiled apologetically at them and continued to assist their kouhai.

Tadashi didn't wait any longer and started to run laps inside the gym.

He tried to focus on practice but he can't help the hairs on the back of his head standing up whenever he feels somebody looking at him.

* * *

Class was, as usual, boring.

But Kei has to pay attention or his grades will go down faster than Hinata and Kageyama's famous quicks.

As he took note of what the teacher was writing on board. He suddenly remembered Yamaguchi's terrified look earlier.

He smirked. Of course, he's satisfied with what his getting. After all of the years him and Yamaguchi spent as friends, that guy still never fails to amaze him.

Or maybe it's just that Tadashi is really gullible and very vulnerable.

Whatever. His plan is going on very well and a few more steps and he'll proceed to his next plan.

He peered at Yamaguchi who's intently listening and jotting down notes to his notebook, completely oblivious of him staring.

Ah, yes. It's going to be intersting.

* * *

Since, Yamaguchi was already in his last year in high school, a third year, his will to improve in volleyball increased even more. Maybe it's becaude he _is_ now a third year that he is striving to prove that he deserves to be in the first six and maybe it's because that he is graduating soon and he won't have the time to play volleyball anymore and he's surely going to miss playing volleyball with everybody.

But for the first time since he decided to give his all every practice, he wanted to go home early for the day. It's actually not the extreme regimen Hachi gave him. It's because the moment he notices Tsukki, he immediately finds a hiding spot for no reason because he's afraid Tsukki might do something funny to him again.

He was almost ready to tell Kageyama that he will skip practice _just_ for today. He even practiced it on lunch time, but once he was already in front of their captain, he forgot the simple line that he practiced.

It felt like Kageyama's face turned scarier by the second that he delays what he's going to say, and Yamaguchi's mouth won't seem to move, no sound is coming from him and he probably looked like a panicked child who broke his mom's favorite vase and now, he has to confess it to his mother.

"...What is it, Yamaguchi-san?" Kageyama was the first one to break the unbearable silence between them.

Oh, the embarrasment. _He_ was the one who called Kageyama because he was supposed to tell him something important but now look at him. _Look_ _at him_.

"Uh- Can I- No... Kageyama, I just want to..." Yamaguchi started to sweat.

I mean what's the big deal of skipping just one practice? He's just going to work hard the next day for it and why is he so afraid of Kageyama now? He wasn't frightened of Kageyama when they were first years, since Kageyama actually isn't really glaring at them.

What the hell is happening to him? Is this because of Tsukki's work?

"Nothing... I just thought that it wasn't really important... He...he." He scratched the back of his head but he just wants to hide right now because of embarrasment. "Sorry for calling you so abruptly."

Kageyama looked at him weirdly and nodded. "...Okay. Are you sure you don't want to tell me something important?"

What the... Kageyama was giving him the chance to actually say what he has to say!

"No, it's fine now. It's not really that important anyways."

"You sure?"

"Totally! Bye, Kageyama." He waved his hand and hurriedly walked on the opposite direction.

What. Is. Happening. To. HIM?

Thankfully, Kageyama seemed to forget what happened earlier because he is busy telling (more like yelling) at their underclassmen to fix their "horrible" forms.

After their usual practice that mostly consists of Kageyama telling them to work hard, Hinata yelling at Kageyama to stop scaring his precious little kouhais, Coach Ukai had enough shit from their captain and ace and make the most out of it by turning their heated argument on a match and dragging everybody along.

Well, at least it's improving everybody's skills.

Yes, everything's going along just fine until he remembers that both him and Tsukki goes home together. Damn.

Yamaguchi cleared his mind for a second. Okay, he doesn't have to hide whenever Tsukki's around. He's his best friend for god's sake! Maybe the kiss and all of those weird antics Tsukki did was just nothing, though the kiss really did surprise him, but nevertheless he should still act normal. Tsukki really liked to play with him in his own ways, but it doesn't mean Yamaguchi will just bend to what he wants, he'll just have to develop a strong mental fortitude and everything will be fine.

Maybe Tsukki will stop his crazy antics too.

Yamaguchi later realized that he was so gullible that he even fooled himself into believing that Tsukki wasn't planning anything, because he really is up to something and even though he wants to get out of it, his blonde bestfriend who seems to have some distant relations to satan himselfalways reels him back in until Yamaguchi find himself fucked. Figuratively. Again.

So they were walking on the same road they've been taking ever since and all seems fine and _normal_ that Yamaguchi thought nothing was really wrong after all. He was just too paranoid and he overthinks sometimes.

Then Tsukki said something so unpredictable that he almost thought that he was walking with a different person, except when he looked, it was still Tsukishima.

"What?" Yamaguchi's mind couldn't process what he just heard.

"I said, I want to kiss you again. Like last time."

The way Tsukki said that he wants to kiss him was like he was just borrowing for a spare pencil. He looked so bored that Yamaguchi almost thought that Tsukki wasn't _really_ saying that he wants to kiss him.

"Y-you want to kiss me again? Why?" he squeaked. Tsukki inched closer to him and took his free hand in his and started to walk in a different direction. Opposite to their houses.

"Wa-Wait. Tsukki, _wait_!" He put all of his weight to his feet to halt. Tsukki also stopped walking and turned back to look at him for an explanation.

"Where are we going?"

Tsukki heaved a sigh and his shoulders slumped. It seems like he was too tired to explain everything to him but then he has to or Yamaguchi won't be able to understand everything that is happening.

"Yamaguchi, I just said it: I want to kiss you again." He said each word with emphasis and slowly as much as he can but Yamaguchi still can't get the gist of all of it.

"Tsukki, I'm sorry, but why?" He thinks he looks pathetic and stupid right now, but whatever. "I mean, we're both guys. _Why_ do you want to kiss me?"

"Because I want to kiss you." Tsukki didn't even thought of what he's going to answer. It's like he knows what he's going to say, no matter what question Yamaguchi might give him pronto.

He realized they were on the next street from his house and the only light illuminating was the street light on their left. He wanted to go there.

"Tsukki, if this is one of your experimentations then count me out. I don't want to take part in any of this."

There was a wall behind him and Tsukki in front of him. Similar thing happened earlier morning and his knees were shaking again.

"Yamaguchi, I didn't say I was messing with you. I really want to kiss you. It's that simple."

He was about to protest again but then he felt Tsukki's face hoarding his line of vision and before he knew it, warm pair of lips landed against his. He shut his eyes because he don't what to do, but surprisinlgly, he didn't push Tsukki away. The moment he kissed him, his brain ceased to function amymore. All of his senses were concentrating on one thing: Tsukki was kissing him.

And he realized a surprising discovery right then and there: he doesn't mind.

 _ **Reviews are highly appreciated.**_

 _ **Credits to the rightful owner of the picture I used as the cover photo.**_


	2. Chapter 2

_**A/N: We shall see what's going on Tsukishima's head regarding the events that shook Yamaguchi's world. I hope I'm not boring you there.**_

 _ **Also, this story won't end at the next chapter. Tsukki tells me that their relationship has a slow build and it won't be great if I rushed to the ending. Yes, I talk with the characters in my mind while writing a story.**_

 _ **Disclaimer: I do not own the characters used in this story. They are just a part of my fictitious 'Cinnamon Bun Squad."**_

 **Passing of Papers in The Middle of Class Causes Detention**

* * *

He never thought that his plan was fool proof or that it was so effective that it immediately worked in just a couple of days. To be honest, he expected it to take effect after a couple of weeks, yet the outcome wasn't that bad at all.

It was a tough time for him to accept what he wanted- who he wanted. He knew that it was against the common ethics they grew up with, but his logic seemed to be not working because instead of abandoning his desires and attraction to that certain individual, he found the most valid reason for the sake of his mind.

It was the 21st century and times surely were changing. The traditions were changed with new ones that agrees with the majority, and it won't be long until their country will be influenced by the Westerns, or if maybe just migrate to some place where it is acceptable.

The fact that Kei actually gave it all a thought and put it into consideration, even though he hasn't made a move to that individual yet made him think that he must've really like him. Well, by him it's his long-time friend, Yamaguchi Tadashi.

Maybe it was just his hormones working because he is a man after all, but he made a plan overnight to make Yamaguchi reciprocate his feelings.

He knew it was just a matter of manipulating the other's thinking, but hey- if it won't work, it means that Yamaguchi's straight and maybe, that'll put and end to this confusion he has.

Yes, he has accepted that his gender preference isn't like the norm, but what can he do if the one he really likes doesn't like him back despite of his plans?

He is smart to know the correct answer.

Tsukishima went home that night, triumphant. Not only did he succeed in his plan, it seems like Yamaguchi might start to have some feelings for him after he kissed him like that earlier.

He must admit that he might have forced Yamaguchi into that kiss. In all honesty, that kiss wasn't really needed. He was supposed to tell Yamaguchi exactly what he feels about him but then he saw that he is in a vulnerable state and that his attention drifted to Yamaguchi's quivering lips and those _cute_ noises that he makes.

The next thing he knew, he already asked for Yamaguchi's permission to kiss him and he disregarded that he asked permission and just went and kissed Tadashi for the second time.

The very first time that he kissed him, he was nervous and his hard was like hammering right to his ribcage, silently pleading to get out. Of course, he hid it well, but he cannot hide his sweating palms of what he was planning to do.

The second time that he kissed Tadashi was better. For a few seconds, he was like a stone unable to move but Yamaguchi surprised him when he faintly replied to his kiss. That, of course, didn't go unnoticed by him and that simple reaction gave him the courage to deepen the kiss.

He was dropping so much hints after he unceremoniously kissed Yamaguchi that he fought the urge to just run and hide because of his actions. It was not in his personality to be so showy of his feelings. He was known as the smart tall boy who doesn't care about you because you don't have any significance in his life, but one person made an exception.

He didn't know when he started to like Yamaguchi in a sort of romantic way, yet he didn't regret every single thing that he had done yesterday and today.

It's not like you get to kiss the one you admire two days in a row. Might as well seize the opportunity and have some balls.

* * *

Tsukishima had another plan going.

After he kissed Tadashi last night, he came into a rather stupid conclusion to ignore talking to Yamaguchi until the latter speaks to him first. He didn't know where he got that idea or why that idea sounded great in his mind last night.

Maybe he's just ignoring Yamaguchi because of his brute action last night.

But Kei wouldn't actually accept that fact so instead, he's acting like nothing's wrong, except maybe that he's ignoring Yamaguchi.

He did this lame act for a whole week and even the people at the club thought that they're fought and he's giving Yamaguchi the cold shoulder. Okay. This was _not_ supposed to happen.

For one whole week, both of them broke their routine of going to and from the school together and if it isn't depressing yet, they also didn't eat lunch together for one whole week. _One whole_ week.

It was too late when Tsukishima realized that his plan was stupid.

He can see that Yamaguchi's confused with what's happening between them, and gives him a look whenever their eyes accidentally meet and he can't help but to feel guilty, yet he can't just talk to him again as if he didn't ignore him for a week. It would probably piss off Yamaguchi.

It was Wednesday when Yamaguchi first talked to him again after their practice. Yamaguchi looked like he was doubting yet still persevered to ask him to go home together.

"Tsukki, wanna go home together?"

He wanted to smile right then and there but restrain himself from doing so. He simply nodded and packed his things. They left the club room with Hinata and Kageyama almost at each other's throat, arguing about something petty that they didn't bother to say good-bye.

Tsukishima knows Yamaguchi completely. He knew what buttons to push and how to properly deal with him. So he didn't expect to be dragged in the nearest empty cul-de-sac the moment they left the school's premises.

"Let's get things straight," Yamaguchi looked at him directly. "Why are you ignoring me, Tsukki?"

Tsukishima found it rather cute when he noticed how Yamaguchi's voice trembled and how his knees are shaking uncontrollably, yet he still straightforwardly asked him his concerns.

"I mean, you were the one who inittiated the kiss. Heck, you even asked for a permission and then after all of that you decide to _ignore_ me?"

"Yamaguchi, I-"

Before he could speak further, Yamaguchi decided to let out all of his distress because the person who cause it was there in front of him. He did something similar when they were freshmen. It was becayse Tsukishima didn't took volleyball seriously and he decided to confront him and open his eyes. Hopefully, thigs will go well like it did before.

"Tsukki," he took a deep breath and glared at him. "Don't think that I don't know what you're planning or what you have already planned because I am perfectly aware of it, and if you're doing this to get a certain reaction out of me. Please stop it because-"

"If you do know exactly what I'm planning, then you must know what I want to do with you, right?"

Of course, Yamaguchi doesn't know a single thing of what he's thinking. He just wants make sure.

"Y-you just want to play with me because, 'I'm fascinating,'" He made quotation marks with his fingers. Tsukishima wants to smile already. Yamaguchi is on the verge of crying.

"Wrong answer, Yamaguchi," Tsukishima smirked and internally sighed in relief. He's glad to know that Yamaguchi haven't caught on what exactly he's planning to do, but then, he kind of wants him to be less dense that he actually was because apparently, he still didn't know that Tsukishima _likes_ him.

"Then what is it?"

"I simply desire you, Yamaguchi." He hoped he conveyed it correctly.

Silence envelops them after Yamaguchi's sudden cry of his confusion of their current situation and when Tsukishima finally told him what his real motive was, it left him dumbstruck.

"...Wait, what?" His eyebrows almost met to form one line. "Did I hear you correctly? Did you just say that you desire me?"

Tsukki verified his question with a nod.

"Yamaguchi, don't be stupid. Do you think I would kiss you two times in a row if I don't actually like you?" He asked.

"Tsukki, don't joke like that. It's not funny." While he looked really determined to know the truth fron him earlier, acting all dominant and all, it was far different from howbhe looked now. "Seriously, do you know what you're talking about?"

Tsukishima was patient to explain everything to Yamaguchi, since he expected that this would happen, but they won't have the time to take it slowly. They still have class tomorrow.

"I already told you that I like you and as much as I want to say it to you until you'll finally understand it, we still have school tomorrow. Just think about what I said and if you want to talk about it with me... you know what to do."

Yamaguchi glared at him intently while fiddling

with the straps of his bag. Tsukishima let him do so and when Yamaguchi left him without saying goodbye, he stayed there for a few good minutes before taking his time going home.

Sure, he can sacrifice a test or two tomorrow.

* * *

It took long enough for Tadashi to talk to Tsukishima about a specific matter that includes both of them, their lips touching and Tsukki's 'confession.' Well, if you can count what happen as a confession then, yeah.

He must have really put a lot of thought into it because he just had been scolded by a teacher and forgot one time that he was the assigned student representative for the day and he forgot his duties.

But with a lot of pep talk by himself to himself and mustering a lot of his courage to talk to Tsukki about the matter, he finally decided to talk to him.

But the problem was, they were still in the middle of class and if he'll try to talk to Tsukki later, all of his found courage fly away and it took him a lot of time for that. It was now or never.

There was only one thing he could think of to let Tsukki know that wanted to talk to him. It was the good ol' passing of paper. He was skeptic about the idea becuase they might get caught but- what the hell. He'll just wing this shit.

He ripped a small section of the very last page of his notebook and scribbled hurriedly, _''Can we talk during lunch? -Yamaguchi'"_

While their teacher wasn't looking, he quickly tapped his seatmate's shoulder to gain his attention and handed him piece of paper while pointing at Tsukki.

His seatmate seemed to get what he was indicating and passed the folded piece of paper to Tsukki.

Tsukki glanced at him and Yamaguchi pointed at the paper, signaling him to read it.

It seems like he finished reading it because he glanced at him again woth a smirk plastered on his face. Yamaguchi saw him do the same he did earlier, ripping a paper from the very last page of his notebook and he wrote something. He was about to hand it over to the same person, when somebody cleared their throat rather too loud.

In an instant, they both subtlety acted like they were taking notes and Tadashi looked in front of the board, only to find that their teacher wasn't there anymore. He looked at Tsukki's direction and was horrified to see their teacher there.

His cheeks flushed when their teacher slowly took two of their notes for each other and opened it. Fortunately, he didn't read it out loud for all of the class to hear but he was still embarrased.

The teacher looked at Tsukki and at him disapprovingly and placed the pieces of papers back at Tsukishima's desk.

"Yamaguchi and Tsukishima, please sort out the papers in my cubicle at the teacher's room at dismissal. You can talk there while doing something productive, other than not listening to my lecture."

"Yes, sensei." They simultaneously replied and didn't dare to look at each other anymore.

It turns out that they won't even have the time to talk at lunch break because Hinata came rushing in their room, dragging Kageyama after him and pleaded Tsukishima's help to teach them physics.

"Tsukishima-kun, we need your help!" Hinata slid the door open with a bang causing the other students to look at their direction. "Yachi told us that you are really, _really_ good at physics and we didn't understand what our teacher just taught us!"

Tsukishima lazily pulled his headphones out of his ears, "You didn't listen to the lecture, didn't you? Don't pull me in just because you're too busy thinking about volleyball even in class."

After a heated bribing and a little bit of threatening by Kageyama that didn't really affect Tsukki, he finally agreed to help them.

And again, Yamaguchi can only wait for another opportunity to talk to him again.

When he said that he is ready to talk to Tsukki, he almost thought about what Tsukki told him that night he confronted him. _Desire._ That's what Tsukki told him. He simply desires him.

He was baffled when he heard it that he stopped thinking afterwards and just said whatever words that's about to come out of his mouth. He even walked out of the scene and left Tsukki all alone.

In his defense, he didn't know Tsukki was actually giving him those kind of signals. He just thought that Tsukki was just bein his usual sadistic self and he hapoens to be the friend who rarely gets mad at you. He's been with the guy for almost a decade and he knows the blonde has some sadistic tendencies that unfortunately always goes to him.

He thought that he'll dislike being kissed by another guy, especially if it wasn't just some drunk random stranger who did it, but it was his closest friend who did that to him and maybe it's one of the factors why he didn't even cringe or felt disgusted when Tsukki kissed him. He just felt surprised and when Tsukki confessed to him, he was unsure what to feel.

He isn't the type to analyze his feelings well, but between him and Tsukki, he thinks he's got the upperhand in this just because he can sympathize with other people and he knows how to read them well, except maybe for Tsukki.

In order for any person to understand Tsukishima, he has to be a graduate in the field of psychology or maybe last a decade of friendship with him.

Yamaguchi's done the latter and he's only got an inkling regarding how Tsukki thinks.

Tsukishima remembered he has detention after dismissal with Yamaguchi so he graciously taught Kageyama and Hinata physics and told their captain that he's got something to do so he won't be able to join practice.

Kageyama didn't let him go easily. He has to agree to double up the regimen he's been following in order to be free during after school's practice.

He skipped practice not because of the detention he got. He can still have high grades even though he had detention. All he needs to do is score high on exam and it won't affect his grades. The reason why he even thought of skipping practice that day is because Yamaguchi will finally give him a proper reply.

He won't admit it loudly, but he's been really looking forward to this day. He's bewn doing enough so-called experiments, using Yamaguchi as his "subject" to know him like the back of his palm.

Yamaguchi was waiting for him outside the teachers' room and straightened his back when he saw him going towards his direction.

"Let's go," he mumbled and excused themselves before opening the door.

"Takeshi-sensei, we're here." Tsukki informed their teacher.

"Ah, Yamaguchi and Tsukishima. Come here."

They walked towards her while she dropped piles of papers on her desk. "Okay, both of you should sort these papers according to the written section and then put them on one of the boxes in that room later," sue pointed the small room in the far left corner of the room. "You two will the only ones who'll be left here because the faculty and staff will have a meeting. I trust you won't something atrocious after the deed you have committed earlier in my class."

She surveyed them and got up from her seat. "I trust that this will serve as a lesson to the both you to listen to my class. After all, you're aiming for best grades to enter the college that you want, yes?"

Yamaguchi nodded frantically and swallowed. Damn, this teacher always scares him.

"Good. Then I shall leave these in your care." She seemed to be in a hurry because she took fast strides and went out of the room.

They stared at the closed door for awhile and Tsukki took the lead by taking half of the papers in the next cubicle and did their task. Yamaguchi followed and started to work as well.

For a couple of minutes, he was already absorbed in his work and even filed each section neatly and alphabetically that he forgot that he's missing a golden opportunity there, of it wasn't for Tsukki who reminded him.

"So, what is so important that you want to talk about that got me in detention?"

Yamaguchi stopped reading the section of the next student's file.

Oh yeah, shit. He forgot what he was supposed to do. He slowly thought of what he's going to say. Carefully choosing the right words in his mind before saying it out loud.

"You know what I wanted to talk about, Tsukki." He peeked at him. He was still doing their job while listening to him.

"I might not give you the clearest answer. I'll probably be vague and out of the topic, but I'll honestly tell you about what I feel." He knew that his voice was brittle and his lips were quivering as he spoke, but what the hell. He started this and he should endure whatever will happen.

"Okay. I'll listen." Tsukki glanced at his direction for a second and went back to segregating the papers.

He inhaled deeply and started to remember everything he had practiced in his room. "Tsukki, you know probably know this already but I really don't know how to act during those times that you suddenly kissed me and then you ignored me all of a sudden and when I confronted you about it, you confessed to me. I felt like you are starting a new test that includes me being your subject again."

Tsukishima looked at him incredulously. He kept saying what was on his mind. Well, he may look like a coward sometimes but once he starts to talk, he'll be able to say everything on his mind.

"I mean if it is, then it's fine with me if you say what is it that you want this early. I won't be mad. Really." He raised both of his hands in the air to emphasize what he said. "But this one has really gone too far, you know."

Tsukki stopped at what he's been doing and looked at him, "Oh, don't worry, I wasn't joking with you when I said that I liked you. I meant what I said, Yamaguchi," he said in a very casual tone. It's as if they were just talking about how Hinata and Kageyama can constantly be stupid idiots who always fight.

"But, I still don't know how to give you a real, proper answer," he groaned. His struggle was so real that he almost gave up explaining and just pulled his hair in frustration. "See, I figured out that I didn't think you kissing me was bad or unpleasant. I'll admit that I was shocked. Who won't be shocked? But the thing is I don't even find it disgusting that a guy is kissing me, but I can't say that I like you, similar to what you feel about me." He was panting when he finished speaking.

He saw Tsukishima contemplating on his answer. He knows because he just adjusted his glasses with his index finger and whenever he does this, he is always thinking about something.

Yamaguchi can't even focus on his work anymore. He was so anxious to know what will Tsukki say.

"So..." Yamaguchi almost jumped on his seat when Tsukishima finally started to speak. "You're not sure about what you feel about me."

It wasn't a question. It was more like Tsukki was talking to himself and was still thinking.

"Why don't we give it a try?" Tsukki finally abandoned the filing of papers and focused his full attention on him

"What do you mean?"

"You just told me. You're not sure. I can't just let you walk away like that, you know. At least now, you're fully aware of what I feel about you, so why don't you yest your feelings?"

"I-I'm not sure that's a good idea," he gulped.

"One week," Tsukishima insisted and continued on his proposition. "Give it like a trial period and once it's over, you can decide what to do."

He was still hesitant to answer. He doesn't know what will be the outcome if they'll really do this.

"It'll be for our benefit, Yamaguchi. Trust me."

Yamaguchi wanted to snort in Tsukishima's statement, but if it means to do the both of them good, then who's he to disagree? He's got to admit that Tsukishima really knows him well, to be able to make him agree with just a couple of words.

"Fine. One week," he sighed. Maybe he's just too soft when it comes to Tsukki.

"Thank you."

It was rare to see Tsukki's genuine smile and it's so out of his character to freely smile like that but here he was, blessed by the heavens to witness Tsukishima Kei's real smile. He thought he was in heaven for a moment until that smile turned into a smirk that he knows so well and before he knew it, their faces were, yet again, almost a hair's breath until their lips come in contact.

"I promise you won't regret it."

 _ **Favorites, follows, and reviews are highly appreciated.**_

 _ **Credits to the rightful owner of the picture I used as the cover photo.**_


	3. Chapter 3

_**Disclaimer: I do not own any of the characters used in the story. They simply fuel my imagination, thus creating this plot.**_

 **The Result of the 'Trial Period'**

After Yamaguchi agreed to Tsukishima's proposition, he immediately started to notice the change on how Tsukki treats him. His actions were sometimes subtle and hard to notice or it'll be the complete opposite of that. He sometimes demands his actions to be noticed and Yamaguchi

That day when they had their detention, they had to put everything they have filed in what it seems like the archives of the teachers, but who would have thought that it was cramped and Tsukki seemed to know everything and made him go in first.

Oblivious to anything, he went in and it was too late for him to protest when Tsukki was already inside, both of them almost had no room to move a single inch.

 _At first, Tsukki acted like it was nothing out of the ordinary. He looked for an empty box and a pen to label the box. They worked quietly for awhile, Tsukki passing the papers by section and him neatly filing it to the box._

 _He suddenly thought that they were really that comfortable in the room. Every time they move, their arms will always make contact. When this happened before Tsukki kissed him, he would've thought nothing about it, but every time their arms will brush, or their hands touch, he feels the hairs on the back of his head stand up. This is how much Tsukki affects him._

 _"Umm... Tsukki? I think this room only needs one person. It's good, I can put everything in a vacant box, you can go outside," he said as properly as he can without his voice shaking. He even laughed for good measure._

 _Tsukki smiled at him. His smile that was labelled as his 'shit-eating' smile, "I don't think you can do it by yourself, Yamaguchi."_

 _He knew it. "Tsukki," he warned him not to push it. It's not like he can do anything to him. He might just walk out of the room._

 _"What is it?" Tsukki playfully replied. He was seriously enjoying this. It's funny how Tsukki can be serious and mischievous after, but whatever it is, he still catches himself playing in his hands. It was always inevitable._

 _"Come on," he sighed exasperatedly. "I didn't sign up for this."_

 _"If I remember correctly, you did agree to what I said earlier," Tsukki responded to him, his smile still on his face._

 _They finished putting all the papers in the box and Yamaguchi inwardly sighed in relief. At least they finished everything before Tsukki could do anything._

 _"Let's go out," Yamaguchi lightly pushed Tsukki towards the door._

 _Tsukki got hold of both of his hands and firmly encircled his hands on his wrists. It wasn't painful, but he can't get his hands back._

 _"What is this?" He tried to pull his hands but the difference in their strength was just too big._

 _"Its part of my plan to make you like me," he explained._

 _Yamaguchi felt his body sweat. He didn't want to be in this position where Tsukki can clearly see him sweat. It wouldn't be attractive to his eyes, or anyone's eyes._

 _"You know this isn't how you woo somebody you like," Yamaguchi remarked. He gave up on retrieving his hands._

 _Tsukishima chuckled, "No, no, no. That wasn't what I was aiming for."_

 _"Yamaguchi, didn't you say you didn't feel that you disliked it when I kissed you?"_

 _He didn't know what to think from Tsukki's question but nevertheless, nodded his head._

 _"So, if I keep kissing you, maybe after some time... maybe you'll like it eventually?"_

 _It's not as if Yamaguchi was given some time to think or even process what he just heard because Tsukki closed the very little distance between them. He leaned in and captured his lips. He made an unusual sound that surprised him._

 _He was sure that his face was sweaty because they've been going in and out of the tiny room for quite a long time to stack the papers accordingly. He really need Tsukki to pull out from their kiss now because if he keeps ups to this, his face will just get sweatier, and it would be an embarrassment._

 _Tsukki did the unthinkable and parted his lips with his tongue and invaded his mouth. He doesn't know what it did to him, but the moment Tsukki explored his mouth, he stopped thinking no matter how he wants to and all of his senses were just focused on the kiss._

He even surprised himself when he found out that he was actually kissing Tsukki back and when they both finished making out, he was out of breath, panting for air and his face looked like shit.

They went home together and it seems that Tsukki clearly wasn't satisfied with what they did earlier and gave him and knee-softening lip-lock again before he entered his house.

He almost can't believe what happened this day. It all happened so fast that Yamaguchi doubts everything. Maybe it was just a fragment of his brain and he's been too tired because of practice lately that he started imagining things.

But then again, if he really is imagining this, it would be that his subconscious is trying to tell him that he is actually attracted to Tsukki, it's just that he can't accept it.

Damn, he can't even understand half of what he's thinking right now.

One proof that told him everything that happened that day was real was his swollen lips. When he went to his room to change his clothes, he accidentally looked at his mirror and his lips caught his attention. It was glistening, like he had just put on lip gloss on his lips and it's slightly bigger.

He had to admit, the kiss that he shared with Tsukki earlier in the cramped room inside the teachers' room was really...

Damn, that kiss just proved that Tsukki is one hell of a great kisser and he wonders if he got a lot of experience in that field. Maybe he kissed a few people, he just doesn't know.

It's not like Tsukki tells him everything. Hell, he doesn't even know if the blonde actually dated the girls that frequently confess to him. He regularly sees those typical cute pink stationary letters anonymously dropped at Tsukki's shoe locker.

People at the club might think that no one would be brave enough or maybe, no one would take interest in the sarcastic blocker of the volleyball club, but the girls who confesses to Tsukki doesn't know his personality. They just see him as the quiet, tall guy who belongs in the college prep class. He wouldn't blame those girls if they took sudden interest on Tsukishima. He was tall, a member of one of the school's sports club, he was smart, and he looks cool having his headphones resting on his shoulders all the time. In other words, he looks like the mysterious guy girls often read in their shoujo manga.

Yamaguchi thought Tsukki won't kiss him again, but boy was he wrong. He really shouldn't trust his gut feeling anymore. It was more of like whatever he thought that was not going to happen anymore, the outcome will be the opposite every time Tsukishima is involved.

When they were with a crowd, Tsukki acted normally, throwing sarcastic comments here and there just to piss people off and he would smile when Tsukki will manage to put on a frown at their classmates' faces. It was his favorite pastime- to piss people off.

He thought everything will be normal, but who was he kidding? He agreed to this trial period thing that Tsukki told him; of course he was to expect that something will happen to the both of them again. Especially when he can't even control his body the moment Tsukki kisses him.

It was strange, but at the end of it, Yamaguchi can't feel regret when he kisses Tsukki back. Instead, he feels satisfaction out of it. Crazy, he knows, but what the hell. He'll just keep this part a secret to Tsukki.

Two days prior to what they agreed to, Tsukki acted normal. And by normal, he meant that when they're alone, he tries to steal a kiss from him whenever he can and always treats him differently that he used to before.

It was lunch time when Tsukki remembered that he didn't bring any lunch with him and Yamaguchi accompanied him to buy bread for lunch. Before they went out of their classroom, the class representative for that day announced that their teacher for their next period won't be able to meet them so they're just going to do a study hall until their next class begins.

After preventing Tsukki from scaring a first-year over limited strawberry shortcake that was just only on sale just for that day, they decided to eat outside, under a tree.

That section of the school was usually unpopular to students because it would take time to return inside the classrooms, but since they have some extra time in their hands, it wouldn't hurt to eat their lunch there. Besides, it's a nice place.

"Tsukki, you should've just given that guy the shortcake. Wasn't he the first one to get that?" His heart almost jumped out of his lungs when he saw a couple of students looking at a very gloomy-looking Tsukki, glowering over a frightened first year who shakily gave him the shortcake.

"He wasn't sure if he was going to eat, but I _want_ to eat it, so I just told him I wanted it." Tsukki shrugged it off like nothing.

"What if a teacher, or much worse, a principal was eating their lunch at the cafeteria? What are you going to do then, huh?"

"Yamaguchi, relax." He chuckled. "Besides, what you just said didn't happen, so what's the use of your 'what ifs'?"

He sighed, "I'm just reminding you that we already got detention yesterday, so it won't be nice if you got caught bullying a first year."

"But I didn't get caught, right? And just so you know, what I did earlier wasn't called bullying," he stated and took a bite from his cake.

Yamaguchi insisted on what he was trying to point out and Tsukishima stared at him.

"What?" he demanded. He was just trying to be helpful and that damn blonde just shrugged him off.

"You know, you're acting like you're really worried about me." A smile slowly formed at Tsukishima's lips. "Are you _that_ worried about me, Yamaguchi? You know if I already made you fall for me that fast then I guess we won't need to do this Trial Period anymore. It'll be useless."

Yamaguchi almost jumped in, and deny what Tsukki just said, but if he did, he'll only make it look like what Tsukishima said was true enough to make him strongly react to it.

"What are you talking about, Tsukki?" He tried to mimic Tsukki's reaction earlier when he just shrugged him off. "I was just saving you from humiliation. Imagine, a third year student going into the principal's office because he was caught intimidating a first year student. What would Suga-senpai say if he was still here?" He 'tsked' and shook his head.

Instead of frowning from what he just said, Tsukki's smile grew wider and it's as if he is smiling from ear to ear, "You really are a bad liar, Yamaguchi."

"Who said I was lying?" He should've known that, that old trick in the book wouldn't trick Tsukki. If you want to outsmart, you should be able to think like him which was almost impossible to do, but he can't admit that, he is, after all, still a man and would like to keep his pride.

"Oh, yeah? You aren't? Want me to prove it?" Tsukki challenged him and leaned in slightly towards his direction.

Of course Yamaguchi knew what Tsukki was going to do when he said he was going to prove that he was lying. He knew very well that it contains both of their lips with a lot of tongue included along the way. He knew this very well, yet instead of backing down from a very obvious trap, he took it like he hadn't experienced one of Tsukki's traps before.

"Prove what? There's nothing to prove, because I'm not lying," he also inclined closer to Tsukki. God, he lost count when they were always caught into this position: faces so close to each other that the only thing to conclude is that they're on the verge kissing.

"We'll see about that," he heard Tsukki mumble and pulled him by his waist and kissed him.

Every time they kiss, it was different. The first one shocked him, the second, it confused him and the kiss on the room last two days was toe-curling. Now this time, it was harsh and unlike how Tsukki usually starts their kiss on a very gentle peck until it builds on something more, this one was very aggressive and he immediately felt Tsukki's tongue inside his mouth, stroking his tongue, urging it to play with him.

Yamaguchi actually didn't know what happened to his brain that time because the only thing he could think of was to prove Tsukki wrong, and it included fighting him with everything Tsukki will do to him. Apparently, kissing was in the list.

He swirled his tongue around Tsukki's earning a groan from the latter and it made him feel proud that he was able to do that Tsukki. He continued to kiss Tsukki, like how Tsukki would kiss him. He concentrated on it so much that he almost forgot that he needs to breathe and only realized it when Tsukki broke away from him. He only went away for a short amount of time because Yamaguchi found his lips on his again.

By the time they stopped kissing, Yamaguchi realized that he was already sitting on Tsukki's lap, Tsukki's hair was tousled- he's guessing that he did that, both of their uniforms were already wrinkled.

"And you said you're not lying," Tsukki's gaze was fixed on his lips and he unconsciously bit it. "Do you want to be kissed again, huh?"

"W-what?" His mind was still fuzzy from the kiss. He didn't get what Tsukishima was implying.

"You're provoking me."

"What? I'm not." What the hell was he talking about? What's he provoking?

"You obviously are." Tsukishima used his thumb to wipe the corner of his lips. "Seriously, don't do that if you don't want to be kissed again."

Yamaguchi didn't reply anymore. It's not that he doesn't want to be kissed by Tsukki again. He wanted to feel Tsukki's soft yet firm lips on his again, but he can't risk it like he did just a minute ago. Somebody might see them and it'll the end for them.

Tsukishima couldn't focus on his assignment because the only thing that's on his mind right now is to make another plan on how he could kiss Yamaguchi again. He wants to smack himself with his book because he's acting like a typical teenage boy who has raging hormones, which he vowed not to be because he deemed those types of guys as fuckboys and he doesn't want to be one of them.

But by the looks of it, he is slowly becoming one of them because the only thing that he could think of is to get into Yamaguchi's pants. Goddamnit.

Yes, he really likes Yamaguchi to the point that he begged asked Yamaguchi to agree to his "Trial Period" Plan. Yesterday, the both of them just had the most intense make out session and mind you, it's just inside their school premises. Fortunately, nobody was there.

He honestly planned to do _something_ there with Yamaguchi. He expected he might get a peck or two but he didn't expect that.

Yamaguchi was really responding to his kisses with the same intensity and increased it when he invaded his mouth. He didn't know what Yamaguchi was thinking that time, but he surely was daring.

To make it short, it was hot.

And that's why whenever Tsukishima would remember that, it will take a lot of self-control from him to stop thinking about things that included a naked Yamaguchi and his bed. He was really starting to be one of those fuckboys.

On the contrary matter, four days has already passed since they started the "Trial Period". Somehow, Tsukishima has seen improvement on Yamaguchi on how he now looks at him. He can sometimes catch him gazing at him and when he was really worried at him yesterday for scaring a first year over strawberry shortcake, but that it was just all that. Something's missing, he can tell but he doesn't know what that is.

He only has three days left and then he has to hear what Yamaguchi's decision, whether he'll be successful on his risky plan or all of it was futile. Tsukishima couldn't think of a plan to actually do that but he feels unease about not doing anything. Yet at the same time, something tells him that everything will be alright.

Tsukishima doesn't really rely on his guts. He wants to see everything happen before his eyes. His instinct telling him alone that everything will go according to his plan doesn't assure him, but the situation he's currently in tells him otherwise.

When the fifth day of their agreement came, he was surprised when Yamaguchi sent him a message early in the morning.

It made his ears hear only the sound of his heart beating frantically, his eyes only focused on the screen on his phone, never blinking. He couldn't even move a muscle. Much more reply to Yamaguchi's message. The only thing he could do was anticipate.

 _From: Yamaguchi Tadashi  
Subject: Tsukki . _

_Tsukki, can we talk later after the morning practice? I want to tell you something._

It was the most common line yet at the same time, the one that can give unpredictable results.

 _ **Reviews, favorites, and follows are always and highly appreciated.**_

 _ **Credits to the owner of the picture used as the story's cover photo.**_


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